One of the most common and costly challenges in the dairy industry is mastitis, an inflammatory reaction of udder tissue due to bacterial, chemical, thermal or mechanical injury. Mastitis adversely affect milk production, milk quality, retail shelf life and increases costs to the farmer in treatment and lost production. It is estimated that mastitis costs the U.S. dairy industry $2 billion per year.
Mastitis may be infectious, i.e. caused by microbial organisms, or noninfectious, resulting from physical injury to the mammary gland. The inflammatory response yields changes in the composition of milk. For example, somatic cell count is increased in mastitis milk.
Severity of mastitis is typically characterized in two stages: sub-clinical mastitis and clinical. Sub-clinical mastitis is characterized by somatic cell counts in the range of 250,000-300,000 per milliliter; clinical mastitis has somatic cell counts in excess of 300,000 per milliliter. High somatic cell count causes a rise in whey protein and a decrease in casein resulting in a considerably lower cheese yields. A shorter shelf life and unpleasant milk flavors result from high somatic cell counts. Higher somatic cell counts are also associated with decreased volume production. Mastitis often begins in one of a cow's teats and, if untreated, typically progresses to one or more of the other teats.
Mastitis typically goes unnoticed until it is rather severe. This is especially the case in dairies that use robotic equipment and methods to milk. Pre-clinical mastitis is generally not detectable by observation.
A variety of technology has been proposed and/or employed to identify mastitis cows or milk. U.S. Pat. Nos. 6,793,624 and 6,348,251 describes the use of near infrared spectroscopy by which milk is subjected to infrared light and a resulting spectral signature is analyzed and compared to the signature for healthy milk. U.S. Ser. No. 11/811,783 describes placing NIR sensors in-line within milking equipment.
U.S. Pat. No. 5,829,381 describes a device for measuring the complex impedance, such as electrical conductance or capacitance, of milk. It does not, however, explore or describe the parameters or a system or process that optimize the use of capacitance as an indicator of mastitis.